Powder coating is a type of coating that is applied as a free-flowing, dry powder. The main difference between a conventional liquid paint and a powder coating is that the powder coating is stored as a solid and does not need to be kept in a liquid form (using such liquids as a water base or solvent) in order to keep the binder and filler particles in suspension. The coating is typically applied electrostatically and is then cured under heat to allow it to flow and form a “skin” around all or part of the substrate. The powder may be a thermoplastic, thermoset, or UV polymer. It is usually used to create a hard finish that is tougher than conventional paint. Powder coating is mainly used for coating of metals, such as household appliances, aluminum extrusions, and automobile and bicycle parts. Newer technologies allow other materials, such as MDF (medium-density fiberboard), to be powder coated using different methods.
There are several advantages of powder coating over conventional liquid coatings:
                1. Powder coatings emit zero or near zero volatile organic compounds (VOC).        2. Powder coatings can produce much thicker coatings in one coat than conventional liquid coatings without running or sagging.        3. Powder coating overspray can be recycled and thus it is possible to achieve nearly 100% use of the coating.        4. Powder coating production lines typically produce less hazardous waste than conventional liquid coatings.        5. A wide range of specialty effects is easily accomplished which would be impossible to achieve with other coating processes.        
While powder coatings have many advantages over other coating processes, there are some disadvantages to the technology. Although the powder is relatively easy to apply in a single thick coating, a single powder coat is not as smooth as a similarly thick liquid paint finish; however, to achieve a similarly thick liquid paint finish it is necessary to apply multiple coats with sanding between each coat. Furthermore, the application of multiple powder coats serves to further increase the thickness of the coating, but does not reliably enhance the visual or tactile smoothness of the powder coated finish.
Many manufacturers of powder coated MDF have taken various steps in the past in order to improve the smoothness of the finish. Methods include:                1. Varying the preheat and cure temperature settings        2. Additional pre-coating sanding, both manual and automated        3. Installation of infrared heaters or UV curing lights at various points in the powder coating line        4. Reformulation of powder used in the coating process        5. Polyester versus epoxy base of the powder coating (chemistry adjustments)        6. Increased fineness of powder grind        7. Repeated sifting of powder during formulation        8. Automated versus hand spraying and measurement of application        
The aforementioned methods have indeed resulted in incrementally increased smoothness relative to previously existing methods. Employing any or all of these methods, however, results in a maximum surface smoothness in the 4-6 range on the PCI scale.
In such industries as furniture and cabinetry, there is growing demand for increasingly smooth finishes. Traditionally, this demand has been met through such finishes as laminates, veneers, vinyl wraps, or liquid paints. These traditional finishes have their own shortcomings and powder coated MDF is frequently a more desirable choice for durability or part design needs. However, it is not possible to achieve similar smoothness in powder coated MDF finishes regardless of content or steps.
Therefore, there exists a need for a method of preparing and top coating an item made of powder coated MDF that enhances visual and tactile smoothness.